“Usual business application relies on lots of data, and that data usual resides in a database. Because data is out of the application thread, accessing it can be much slower. If external data is on a hard drive (and it usually is), accessing it can be thousands of times slower than accessing data in application memory. The great thing about cached data is that not only it will be few thousand times faster, but it will also scale much better under heavy load than your poor database.”

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